2006 Ford Mustang GT - Project Mustang Cam Swap

We write about cam swaps all the time in Car Craft, but we’ve never covered swapping cams on a Modular Ford before. Way back in the Oct. ’11 issue, we documented the Trick Flow head and cam swap on our Project Panther’s SOHC 4.6, but we did that job while the engine was out of the car being rebuilt.

It turns out cam swap with the engine in the car really isn’t that bad. We brought Editor Glad’s 2006 Ford Mustang GT to Greg Monroe at Racers Edge Tuning in Downey, California, where he and his crew got the job done in a day, with the car running on the dyno the next morning.

Yes, these guys are pros, and this is what they do for a living, but you can do this at home over a weekend. It didn’t require any exotic tools, but you will need to have a decent balancer puller. You’ll also need a way to re-flash the ECM, so plan to buy a tuning device, and schedule a day with your local dyno shop.

Once done, you can expect some impressive power gains. You’ll have to force yourself to not do burnouts everywhere you go.

Parts List

Description

PN

Source

Price

Cloyes timing-chain tensioner, left

5338

Rock Auto

$34.99

Cloyes timing-chain tensioner, right

95339

Rock Auto

36.99

Cam bolt

3L3Z-6279-DA

Your local ford dealer

19.99/each

Comp camshafts

127055

Comp Cams

729.95

SCT X3 Power Flash programmer

3000

Racers Edge

350.00

Cam Specs

The old cams

PN

Duration at 0.050

Lift

LSA

XE 6251-309994

221/240

0.470

110

The new cams

PN

Duration at 0.050

Lift

LSA

XE253LH-15

214/231

0.450-inch

115

Before tearing into the engine for the cam swap, Monroe did a baseline pull. To refresh your memory, our Mustang is equipped with Ford Racing Performance Parts’ Big Boost supercharger kit (read that install in our Sept. ’11 issue). Since then, we dropped in an Aluminator crate engine, which came with Ford Racing’s Hot Rod cams. With specs of 221/240 degrees of duration at 0.050-inch lift and a 110-degree lobe-separation angle, these cams were more suited to a naturally aspirated engine, not necessarily a supercharged street-car engine. The narrow lobe-separation angle and late-closing exhaust bleeds off the intake charge at low rpm, which gave the ECM fits as it tried to maintain a decent idle speed and manage low-rpm driveability. The combination worked nicely above 5,000 rpm, however, and on RET’s chassis dyno, our Mustang posted peak numbers of 514 hp and 452 lb-ft at the wheels.

RET’s Beni Holguin started by draining the coolant from the radiator and engine block.

Next, he removed the belt, water-pump pulley, and harmonic balancer using this three-jawed puller he bought from the Matco truck. It’s for an LS engine, but works on Fords, too.

Both the A/C compressor and power-steering pump are bolted to the timing cover, so Beni removed the fasteners but left the components sitting in the engine compartment.

Beni disconnected the wires to the fuel injectors, coils, sensors—all the stuff you’d expect. But he also removed the battery and disconnected the starter wiring and the big connector going into the fuse box. This picture shows you why; disconnecting those seemingly unrelated components allowed him to move the entire front harness out of the way, giving him unfettered access to the top of the engine.

This is what the cam drive system on a Modular engine looks like. The toothed wheel on the crankshaft provides the signal for the crank-position sensor. Also visible are the cam phasers on the fronts of the cam gears. They provide approximately 10 degrees of cam-timing adjustment under various driving conditions.

To remove the timing chains, Beni had to relieve the pressure applied by the tensioners. He collapsed the tensioner’s hydraulic plunger with adjustable pliers, then removed the tensioners and tensioner arms. You can leave the chain guides in place (the flat, plastic piece near the top if this picture), because they are on the slack side of the chain and don’t interfere with the removal or installation of the chains.

The tensioners can be difficult to remove because they are a tight fit to the chain, even with the plunger collapsed. Beni installed these clips to hold the plunger in, and he had to turn the crankshaft a few degrees by hand to get the driver-side tensioner out. The plunger clips come on new tensioners when you buy one, but we haven’t seen any for sale just by themselves.

Be sure to inspect the rubber O-ring on the backside of the tensioner, as they often develop leaks. Sure enough, ours had a tear in it.

Whether or not you’ve got leaky tensioners, a good upgrade is to replace the plastic tensioners (found on newer Modular engines, from about ’99-up) with the older-style steel tensioners. Their machined sealing surface eliminates the need for an O-ring, thus eliminating a potential leak path. Search Rock Auto for a ’99-or-older, 4.6-powered car (Crown Victoria, Mustang, F-150); they sell for about $35 apiece. Note that the right and left side are different part numbers and can’t interchange.

With the chains out of the way, Beni was able to unbolt the cam towers and remove the cams.

Be sure to keep the cam-tower caps in order. Just like main-bearing cams, the caps are machined to fit together with their corresponding tower. If you mix them up, the cams may not turn freely.

The cam gears and phasers are held to the cams by these one-time-use, torque-to-yield bolts. Replace them with new ones (Ford PN 3L3Z-6279-DA) prior to installing new cams. Buy two because they’re sold individually.

This picture shows the valve arrangement for a 3V Modular engine—two intake valves with the exhaust valve in between them. The roller-cam followers are held in contact with the cam lobe by both valvespring pressure and the hydraulic-lash adjusters opposite the valvesprings (but hidden under the cam followers in this picture).

After applying the supplied assembly lube to the cam towers, Beni dropped in the new Comp cams with the timing marks roughly positioned for TDC on the No. 1 piston. The new cam bolts are installed but are only finger-tight at this point. Beni will torque them once the timing chains are installed.

Tightening the cam tower caps should initially be done by hand, then torqued to 90 lb-in, starting from the center cam cap and working out. Tightening the caps will cause some of the valves to open, so you’ll feel resistance from the valvesprings as you do this. As you tighten, the cam will fully seat into the cam towers. Watch to make sure none of the cam followers slip off their respective cam lobes during this process.

Before installing the timing chains, Beni rotated the crank until the timing mark on the crank gear was in the 6 o’clock position.

The timing chains have two dark links—one for the crank-gear timing mark, and another for the cam-gear timing mark. You may have to turn the cam slightly, but once the timing marks match the links on the chain, your valve timing will be correct.

After the driver-side chain and tensioner were installed, Beni checked the crank-gear timing mark to make sure it hadn’t shifted position.

With the passenger-side chain installed, Beni replaced the tensioner arm and installed the new tensioner, torqueing it to 20 lb-ft.

Cam-holding tools are available, but they usually run on the order of a couple hundred dollars. Beni did things in a less expensive manner, modifying a socket to fit the hex at the rear of the cams and having a co-worker hold the cams as he torqued them to 45 lb-ft. To prevent these bolts coming out, Beni applied a generous amount of thread locking compound to the cam bolts.

Beni applied a bead of RTV sealant along the bottom of the timing cover and at the parting lines between the heads and engine block, then reinstalled the timing cover, making sure all the bolts went back in the right places.

After that, it was a matter of plugging all the wiring back up, replacing the radiator hoses, attaching the A/C and power-steering pump, and reinstalling the balancer. Beni used this balancer installation tool manufactured by Lisle, which fits a variety of applications.

Beni used this balancer installation tool manufactured by Lisle, which fits a variety of applications.

The car started and ran after the cam swap when Beni turned the key, even with the different cam specs. They let the engine come up to operating temperature and bled the cooling system at the bleeder screw in the coolant crossover to make sure all the air pockets were out of the engine. Then Monroe strapped it to his chassis dyno and loaded a basic tune-up based on the cam’s specs, the size of the MAF sensor and throttle-body, rear-axle ratio, and fuel-injector flow rate. He uses SCT Pro Racer tuning software to write the program, which gets loaded into the car’s ECM via a SCT X3 Power Flash handheld programmer. He made a few dyno pulls, making small timing and fuel adjustments to get the car dialed in.

Even though the replacement cams were smaller than the ones we removed, Greg was able to coax a couple more horsepower out of the combination compared with the baseline numbers, with peak numbers after the cam swap of 507 hp and 446 lb-ft.